Recommendation for eliminating or mod the exhaust tube on right exhaust manifold

[1978 NYB]

I'm just about ready to upgrade the intake system of my '78 Ny'er with a 400. I know from the posts on this forum about Thermoquad's being the recommended carb. I'm going to keep all the old stuff and if the Eddie stuff doesn't work out I'll get the Quad rebuilt by the guy Commando recommended and put it back on. I have a Eddie 2186 intake, 1406 carb, carb & txsm adapters, eddie 14x3 air cleaner. All will fit under the hood. I also have the Mopar Performance aluminum valve covers. Left side set up for PCV and right side set up for breather cap and 3/4" hose to the bottom plate of the Eddie air cleaner adapter. My problem is that tube on my '78 400 that goes from the rear of the right side exhaust manifold to a check valve and then to the bottom of the factory air cleaner. What recommendations do you have to eliminate or modify that tube.

 

[commando1]

Professor Formal is stumped.
Can't recall seeing one.

 

[1978 NYB]

I'll take a picture and try to post. I've never seen something so strange. Sounds like the muffler fell off when unplugged from the air cleaner.

 

[commando1]

Pics of it will definitely help.
The Emissions section in my FSM show nothing remotely like that.
The sticker on the radiator support - Does it say it's a Caly-for-ny-aye engine?

 

[1978 NYB]

I don't think it's a Cali emission car. no indication on the radiator support. The emission tag is 4100968. I took a picture of that sticker, the vacuum hose diagram and the fender tag. I'll post them now as I'm hoping to have a flashback on posting pics. It does have 2 vacuum canisters and has a fuel filter that has an extra vent line (or return) to the fuel tank.

 

[1978 NYB]

I coudldn't get any closer to the rear of the manifold. It's that 1/2" tube with one bolt on the bottom side of the tube that's bolted to the rear of the mainifold.

 

[1978 NYB]

The 3rd picture shows where that tube comes over the intake and goes into that check valve then it goes into the bottom of the air cleaner base. I don't know if all 400's have this or just 1978's.

 

[1978 NYB]

Here's the emission sticker's and fender tag.

 

[commando1]

I have never seen that before but I have yet to see it all.
The only way to figure out why it's there is to figure out which way the check valve works.
1. to prevent air being DRAWN from the air filter to the exhaust, or....
2. to prevent exhaust being DRAWN into the ar filter.
We can then take it from there.
Boy! a '78 FSM would be nice now, wouldn't it?
My '76 shows nothing even close.

 

[has2bmopar]

I have always seen this as a Y pipe connecting to the rear of both exhaust manifolds to introduce O2 to the manifolds. The same theory as the catalytic converter, by means of a belt driven air pump.

If you have also eliminated the air pump and converter or if the internals are gone from the converter there will be no function for these tubes. You can unbolt them, cut them off, and weld a plug in them so they are sealed, or get an older set of exhaust manifolds.

Depending on the level of dictatorship in your state, you may want to check if there will be any issues for eliminating emmisions equipment, but with the age of this I wouldn't expect any problems.

Also if your aftermarket intake is a square bore you can save the majority of hieght gained by an adapter plate by using your existing Edelbrock with a 1/4" isolator gasket. The only issues I have had with the Edelbrock AFB style carbs were the flat needle and seat design. If you put the later spring loaded units in or the Carter style with the normal pointed needle and seat, I don't forsee you having problems with the carb you have. I have had exellent luck with the Carters and Edelbrocks, but you should run an isolator to keep it cooler.

 

[1978 NYB]

It's called an aspirator valve. All 78's with a cat has it. It uses exhaust pressure pulsation to draw air into the exhaust system. It draws fresh air from the air cleaner past the one way check valve (aspirator). I don't have a cat anymore. I have duals from the manifolds and flowmasters. My plan was to just eliminate that whole tube and check valve assembly since I don't need it and I won't be able to connect it to the air cleaner after upgrading the intake/carb. I don't know if you can see the one bolt mounting that tube to the rear of the manifold. I'm just leary of trying to take that bolt out of the exhaust manifold that has been there for 34 years without breaking it. I plan on hitting it with PB blaster for a week to loosen it up. I was hoping someone else has an easy mod for this. If I get it off, I was thinking of cutting it off flush and cover the hole and weld it and bolt it back on.

 

[goodneighbour]

It's called an aspirator valve. All 78's with a cat has it. It uses exhaust pressure pulsation to draw air into the exhaust system. It draws fresh air from the air cleaner past the one way check valve (aspirator). I don't have a cat anymore. I have duals from the manifolds and flowmasters. My plan was to just eliminate that whole tube and check valve assembly since I don't need it and I won't be able to connect it to the air cleaner after upgrading the intake/carb. I don't know if you can see the one bolt mounting that tube to the rear of the manifold. I'm just leary of trying to take that bolt out of the exhaust manifold that has been there for 34 years without breaking it. I plan on hitting it with PB blaster for a week to loosen it up. I was hoping someone else has an easy mod for this. If I get it off, I was thinking of cutting it off flush and cover the hole and weld it and bolt it back on.

If it was me I`d just get another log from something older put it on and eliminate it all together!

 

[has2bmopar]

Bingo, I guess I didn't specify to plug and weld your existing flanges. I have never broken these bolts off, but I have also presoaked them.

 

[1978 NYB]

I have always seen this as a Y pipe connecting to the rear of both exhaust manifolds to introduce O2 to the manifolds. The same theory as the catalytic converter, by means of a belt driven air pump.

If you have also eliminated the air pump and converter or if the internals are gone from the converter there will be no function for these tubes. You can unbolt them, cut them off, and weld a plug in them so they are sealed, or get an older set of exhaust manifolds.

Depending on the level of dictatorship in your state, you may want to check if there will be any issues for eliminating emmisions equipment, but with the age of this I wouldn't expect any problems.

Also if your aftermarket intake is a square bore you can save the majority of hieght gained by an adapter plate by using your existing Edelbrock with a 1/4" isolator gasket. The only issues I have had with the Edelbrock AFB style carbs were the flat needle and seat design. If you put the later spring loaded units in or the Carter style with the normal pointed needle and seat, I don't forsee you having problems with the carb you have. I have had exellent luck with the Carters and Edelbrocks, but you should run an isolator to keep it cooler.

There's only one tube on the right manifold. I don't know about other years, but '78 400's don't have air pumps. It's the only Mopar engine that doesn't have one. From what I understand, that tube and check valve draws clean air from the air cleaner and flows through the exhaust manifold and goes to the cat.

I called Edelbrock some time ago, and the adapter plate (9132 I think) that comes with the Performer manifold kit is the preferred installation with a standard gasket on both sides using an Eddie carb. That 3/4" aluminum adapter is only needed to bolt on an Eddie carb to a stock cast iron intake according to them.

Maryland is a classic Mopar friendly state. I have historic tags which means no emission checks or tests and no restrictions on mods.

Thanks.

 

[1978 NYB]

I soaked it overnight with Sea Foam Deep Creep and it came apart easily. Threads in perfect condition too. I'm suprised since it was screwed into the exhaust manifold for 34 years.

 

[70NPORT]

There's only one tube on the right manifold. I don't know about other years, but '78 400's don't have air pumps. It's the only Mopar engine that doesn't have one. From what I understand, that tube and check valve draws clean air from the air cleaner and flows through the exhaust manifold and goes to the cat.

I called Edelbrock some time ago, and the adapter plate (9132 I think) that comes with the Performer manifold kit is the preferred installation with a standard gasket on both sides using an Eddie carb. That 3/4" aluminum adapter is only needed to bolt on an Eddie carb to a stock cast iron intake according to them.

Maryland is a classic Mopar friendly state. I have historic tags which means no emission checks or tests and no restrictions on mods.

Thanks.

1978NYB, are MD emission regs as draconian as NJ emissions? I failed a few weeks ago and I've been thinking of getting historic tags to eliminate going thru all that nonsense again. They nailed me for too much CO2.
Are there any mileage stipulations on historic tags?

 

[1978 NYB]

The language in the MVA website doesn't say anything about specific annual mileage. I have a lot of friends with historic tags and no one has been hassled - ever. I'm sure if you are a local nuisance in Maryland, i.e., open headers, racing on the streets, etc., I'm sure the police would scrutinize your historic tags. I drive through numerous security check points on the military base where I work every day and when I'm driving the NYB (as often as weather permits) all I get is great comments and a smile.